Method for electrostatic coating of a medical device

Abstract

A method for electrostatic coating of medical devices such as stents and balloons is described. The method includes applying a composition to a polymeric component of a medical device which has little or no conductivity. The polymeric component could be a material from which the body or a strut of the stent is made or could be a polymeric coating pre-applied on the stent. The polymeric component could be the balloon wall. A charge can then be applied to the polymeric component or the polymeric component can be grounded. Charged particles of drugs, polymers, biobeneficial agents, or any combination of these can then be electrostatically deposited on the medical device or the coating on the medical device. One example of the composition is iodine, iodine, iodide, iodate, a complex or salt thereof which can also impart imaging capabilities to the medical device.

Description

CROSS REFERENCE[0001]This application is a continuation-in-part of U.S. application Ser. No. 12 / 121,692, filed on May 15, 2008, the entire content of which is incorporated by reference.FIELD OF INVENTION[0002]The present invention is related to methods of electrostatically coating a medical device, more specifically a stent or a balloon. More particularly, the present invention is related to methods of electrostatically depositing drugs or active agents on polymeric stents, polymeric coatings on stents, polymeric dilatation balloons, or other medical devices.BACKGROUND OF THE INVENTION[0003]In percutaneous transluminal coronary angioplasty (PTCA), a balloon catheter is inserted through a brachial or femoral artery, positioned across a coronary artery occlusion, and inflated to compress against atherosclerotic plaque to open, by remodeling, the lumen of the coronary artery. The balloon is then deflated and withdrawn. Problems with PTCA include formation of intimal flaps or torn arter...

AI Technical Summary

Problems solved by technology

Problems with PTCA include formation of intimal flaps or torn arterial linings, both of which can create another occlusion in the lumen of the coronary artery.

Moreover, thrombosis and restenosis may occur several months after the procedure and create a need for additional angioplasty or a surgical by-pass operation.

However, dipping and spraying techniques requires for large amounts of drugs and solvents to be used which can be hazardous for the operator and the environment.

The current dipping and spray techniques are very wasteful methods of coating medical devices, most particularly when very small geometrical structures like stents are being coated.

For example, during the spray application of the drug composition, a majority of the coating material, including a drug, is wasted as only a fraction of the spray flux is intercepted by the stent struts.

Moreover, dipping and spray coating processes can tend to promote a great deal of coating defects.

Coating defects can include an uneven thickness in stent and balloon coating, which would in effect translate into uneven distribution of the drug across the surface body of the medical device.

Stent coating defects can also include “webbing” between stent struts (over the gaps or opening between the struts) or coating “pools” which are excessive gatherings on the stent struts.

Webbing and pooling can lead to adverse biological responses when the stent is implanted.

Finally, dipping and spray coating processes can lead to manufacturing inconsistencies between batches of stents and balloons during production.

Lack of control in the coating process can lead to, for example, an unpredictable drug distribution and inconsistent coating topography between different batches of stents or balloons.

An unpredictable drug distribution means that some stents can have more drug than was intended to be deposited and some can have significantly less.

A large discrepancy in what was intended to be deposited is definitely unwanted since it will not be know with accuracy how much drug a patient will receive.

However, stents that have been pre-coated with a polymer, for example a polymer primer without a drug, or those that are made from a polymer provide for electrically non-conductive surfaces and cannot be grounded, biased or polarized for electrostatic deposition of drugs.

Furthermore, all dilatation balloons are composed of polymeric materials, and as such are generally non-conductive.

These polymers also cannot be grounded or biased to allow electrostatic deposition.

Alternatively, the surface of the device is wet during the application of the charged drug to the device.

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